In the safety-critical systems, potential hazard may lead to catastrophic accidents, therefore it is greatly significant to analyze its influence. There are two causal logic relationships from risks to accidents that are deterministic and non-deterministic relationship. The former can be analyzed by event tree and fault tree. However, due to the latter's uncertainties and lack of data, Bayesian network could be applied as an appropriate tool. However, it is a difficult task to determine the conditional probability table. This paper proposes a new allocation method of conditional probability based on fuzzy logic. Combined with the risk model of influencing factors established, Bayesian network is used for quantitative analysis. Finally, the feasibility of proposed method is evaluated through case study.